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Hydrophobicity vs hydrophilicity: Effects of poly(ethylene glycol) and tert-butyl alcohol on H2O as probed by 1-propanol

TitleHydrophobicity vs hydrophilicity: Effects of poly(ethylene glycol) and tert-butyl alcohol on H2O as probed by 1-propanol
Publication TypeJournal Article
Year of Publication2005
AuthorsMiki, K, Westh, P, Koga, Y
JournalJournal of Physical Chemistry B
Volume109
Pagination19536-19541
Date PublishedOct
Type of ArticleArticle
ISBN Number1520-6106
Keywords25-DEGREES-C, ALKANE-MONO-OLS, AQUEOUS-SOLUTIONS, EXCESS CHEMICAL-POTENTIALS, GLYCEROL, HOFMEISTER SERIES, MIXING SCHEMES, MOLECULAR-ORGANIZATION, PARTIAL MOLAR ENTHALPIES, THERMODYNAMIC APPROACH
Abstract

The enthalpic interaction between 1-propanol (IP) molecules, H-1P- 1P(E), was evaluated in 1P-poly(ethleneglycol) (PEG)-H2O and 1P-tert-butyl alcohol (TBA)-H2O ternary mixtures. The model-free and experimentally accessible quantity, H-1P-1p(E), indicates the effect of an additional 1P on the actual enthalpic situation of 1P in the mixture. It was shown earlier that the composition dependence of H-1P-1P(E) reflects the process how 1P modifies H2O. This H-1P-1P(E) pattern changes in the presence of a third component, PEG or TBA. The effects of PEG or TBA on the molecular organization of H2O were elucidated from these induced changes. Together with previous similar studies for the effects of methanol (ME), 2-propanol (2P), ethylene glycol (EG), and glycerol (Gly), we suggest a method and hence a possible scaling for sorting out hydrophobicity vs hydrophilicity of these alcohols by the changes induced to the loci of the maxima in H-1P-1P(E). We show that hydrophilicity scales with the number of oxygen, regardless of whether O is the ether -O- or the hydroxyl -OH. Hydrophobicity also scales with the number of carbon atoms for alcohols without a methyl group. For those with methyl groups, the hydrophobicity seems proportional to the total number of carbon with a different proportionality factor from those without methyl group.

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